首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2568994篇
  免费   201231篇
  国内免费   3982篇
耳鼻咽喉   36398篇
儿科学   87239篇
妇产科学   72640篇
基础医学   365348篇
口腔科学   73244篇
临床医学   228439篇
内科学   501823篇
皮肤病学   55094篇
神经病学   206225篇
特种医学   102519篇
外国民族医学   1065篇
外科学   390153篇
综合类   60389篇
现状与发展   4篇
一般理论   905篇
预防医学   199790篇
眼科学   58870篇
药学   192804篇
  5篇
中国医学   4775篇
肿瘤学   136478篇
  2018年   25224篇
  2016年   21491篇
  2015年   24570篇
  2014年   34120篇
  2013年   52327篇
  2012年   71198篇
  2011年   75282篇
  2010年   44829篇
  2009年   42607篇
  2008年   72022篇
  2007年   76439篇
  2006年   77364篇
  2005年   75256篇
  2004年   73732篇
  2003年   70814篇
  2002年   69367篇
  2001年   120138篇
  2000年   124649篇
  1999年   105880篇
  1998年   29216篇
  1997年   26489篇
  1996年   26742篇
  1995年   25789篇
  1994年   24335篇
  1993年   22782篇
  1992年   86332篇
  1991年   84193篇
  1990年   82415篇
  1989年   79019篇
  1988年   73329篇
  1987年   72217篇
  1986年   68148篇
  1985年   65734篇
  1984年   49288篇
  1983年   42228篇
  1982年   24801篇
  1981年   22336篇
  1980年   20636篇
  1979年   46221篇
  1978年   32257篇
  1977年   27192篇
  1976年   25595篇
  1975年   27295篇
  1974年   32870篇
  1973年   31665篇
  1972年   29134篇
  1971年   26994篇
  1970年   25101篇
  1969年   23327篇
  1968年   21284篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
42.
Evidence continues to grow on potential environmental health hazards associated with engineered nanomaterials (ENMs). While the geno- and cytotoxic effects of ENMs have been investigated, their potential to target the epigenome remains largely unknown. The aim of this study is two-fold: 1) determining whether or not industry relevant ENMs can affect the epigenome in vivo and 2) validating a recently developed in vitro epigenetic screening platform for inhaled ENMs. Laser printer-emitted engineered nanoparticles (PEPs) released from nano-enabled toners during consumer use and copper oxide (CuO) were chosen since these particles induced significant epigenetic changes in a recent in vitro companion study. In this study, the epigenetic alterations in lung tissue, alveolar macrophages and peripheral blood from intratracheally instilled mice were evaluated. The methylation of global DNA and transposable elements (TEs), the expression of the DNA methylation machinery and TEs, in addition to general toxicological effects in the lung were assessed. CuO exhibited higher cell-damaging potential to the lung, while PEPs showed a greater ability to target the epigenome. Alterations in the methylation status of global DNA and TEs, and expression of TEs and DNA machinery in mouse lung were observed after exposure to CuO and PEPs. Additionally, epigenetic changes were detected in the peripheral blood after PEPs exposure. Altogether, CuO and PEPs can induce epigenetic alterations in a mouse experimental model, which in turn confirms that the recently developed in vitro epigenetic platform using macrophage and epithelial cell lines can be successfully utilized in the epigenetic screening of ENMs.  相似文献   
43.
In the 6th Basic Plan for Long-Term Electricity Supply and Demand (6th BPE) for Korea, for the first time, the environmental costs of air pollution caused by oxides of sulfur (SOx), oxides of nitrogen (NOx), and particulate matters (PM) from power plants were estimated and included. However, several deficiencies in evaluating the environmental costs were found. In this study, (1) the validity of the environmental costs used in the 6th BPE was assessed, (2) a systematic approach was suggested and used to improve the environmental costs estimation, and (3) the sensitivity of the cost of generating electricity to the environmental costs by fuel type with the proposed approach was discussed. We found that the applied environmental costs used in the 6th BPE did not fully include the demographic characteristics of Korea. By applying more realistic parameter values, it was found that the newly estimated environmental cost was about 23 times higher than the cost estimated in the original 6th BPE for coal-fired power plants and about 1.5 times higher for liquefied natural gas (LNG)-fired power plants, suggesting that LNG-fired power plants are more economical if using more realistic environmental costs. Thus, it is critical to check the validity of parameter values when calculating environmental costs.  相似文献   
44.
45.
46.
Abstract

Objective: To understand the origin of extremely high gonadotropin levels in a perimenopausal woman.

Methods: A 52-year-old woman with a 2?months of amenorrhea followed spontaneous menstrual cycles recovery was referred to our outpatient clinic with elevated follicle-stimulating hormone (FSH, 483 mUI/ml), luteinizing hormone (LH, 475 mUI/ml) and prolactin (PRL, 173?ng/ml). She was known to take levosulpiride. The gonadotropin levels did not fit with the clinical features.

Results: A gonadotroph tumor was ruled out. Further analysis confirmed constantly high FSH, LH and PRL levels. The measurements were repeated using different analytical platforms with different results. After serial dilutions, nonlinearity was present suggesting an immunoassay interference. After post-polyethylene glycol recovery, hormone levels appeared in the normal range. Anti-goat antibodies were recognized in the serum of the patient.

Conclusions: This case report shows a case of falsely abnormal high gonadotropin and PRL levels in a woman during menopause transition. In the clinical practice the evaluation of gonadotropin profile is not recommended at this age, but the abnormal levels stimulated further evaluation. An interference in the assay due to anti-goat antibodies resulted in abnormally high level of FSH and LH. A strict collaboration between clinicians and the laboratory is needed, when laboratory findings do not correspond to clinical findings.  相似文献   
47.
48.
49.
50.
This study used the National Survey of Ambulatory Surgery (NSAS) database to measure the incidence of and risk factors for symptoms in the ambulatory surgery center and problems within 24 h after isolated carpal tunnel release (CTR). The NSAS contained records on 400,000 adult patients with carpal tunnel syndrome who were treated with CTR in 2006, based on ICD-9 codes. The type of anesthesia used and factors associated with symptoms and problems were sought in bivariate and multivariable statistical analyses. The mean duration of the procedure was 16 ± 8.8 min. Only 5 % were performed under local anesthesia without sedation, 45 % with IV sedation, 28 % regional anesthesia, and 19 % general anesthesia. Symptoms in the ambulatory surgery center or a problem within 24 h after discharge were recorded in 10 % of patients, all of them minor and transient, including difficulties with pain and its treatment. The strongest risk factors were male sex, age of 45 years and older, and participation of an anesthesiologist. Local anesthesia and regional anesthesia were associated with more perioperative symptoms and postoperative problems. Most CTR are performed with some sedation in the United States. CTR is a safe procedure: one in 10 patients will experience a minor issue in the perioperative or immediate postoperative period.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号